Anti-viral azide-containing compounds

ABSTRACT

Methods of using azide-modified biomolecules, such as fatty acids, carbohydrates and lipids, to treat a plant or an animal infected with a virus or to inhibit infectivity of a virus, such as the human immunodeficiency virus, are provided. Also provided are methods of labeling a human immunodeficiency virus with an azide-modified biomolecule, such as a fatty acid, a carbohydrate, or an isoprenoid lipid. The azide-modified biomolecules may be combined with a pharmaceutically acceptable excipient to produce a pharmaceutical composition, optionally containing another anti-viral agent and/or a delivery agent, such as a liposome.

BACKGROUND

Viral infections account for significant morbidity and mortality in humans and animals. In addition, viral infections also result in significant agricultural losses, with plant viruses causing an estimated $60 billion in lost crop yields throughout the world each year. Although significant resources have been dedicated to identifying compounds having anti-viral properties, viral infections continue to present a significant risk to human health and agriculture.

In addition, the usefulness of most existing anti-viral treatments is limited by the development of multidrug resistance, poor efficacy, and/or toxicity. In fact, many anti-viral treatments are highly toxic and can cause serious side effects, including heart damage, kidney failure and osteoporosis. Other challenges include creating a drug that is broadly applicable in combating many different types of viral infections, which can be particularly important in the treatment of immunocompromised individuals.

One virus in particular, the human immunodeficiency virus (HIV), remains a global pandemic despite the development of antiretroviral drugs targeting HIV. As of 2007, it was estimated that more than 33 million people were infected with HIV, and HIV associated diseases represent a major world health problem. HIV is a retrovirus that infects CD4⁺ cells of the immune system, destroying or impairing their function. As the infection progresses, the immune system becomes weaker, leaving the infected person more susceptible to opportunistic infections and tumors, such as Kaposi's sarcoma, cervical cancer, lymphoma, and neurological disorders. The most advanced stage of HIV infection is acquired immunodeficiency syndrome (AIDS). It can take 10-15 years for an HIV-infected person to develop AIDS. Certain antiretroviral drugs can delay the process even further.

Although much effort has been put forth into designing effective therapeutics against HIV, currently no curative anti-retroviral drugs against HIV exist. Several stages of the HIV life cycle have been evaluated as targets for the development of therapeutic agents (Mitsuya, H. et al., 1991, FASEB J5:2369-2381). One area of focus has been the HIV reverse transcriptase enzyme. Reverse transcriptase copies the HIV, single stranded RNA genome into double-stranded viral DNA. The viral DNA is then integrated into the host's chromosomal DNA where the host's cellular processes, like transcription and translation, are used to produce viral proteins and ultimately new virus particles. Therefore, interfering with reverse transcriptase inhibits HIV's ability to replicate. One class of reverse transcriptase inhibitors is nucleoside analogs, such as Zidovudine (AZT), Didanosine (ddI), Zalcitabine (ddC), and Stavudine (d4T), Lamivudine (3TC), Abacavir (ABC), Emtricitabine (FTC), Entecavir (INN), and Apricitabine (ATC) (Mitsuya, H. et al., 1991, Science 249:1533-1544; El Kouni, Curr Pharm Des, 2002, 8:581-93; Sharma et al., Cur Top Med Chem, 2004, 4:895-919). Another class of reverse transcriptase inhibitors is nucleotide analogs, such as Tenofovir (tenofovir disoproxil fumarate) and Adefovir (bis-POM PMPA) (Palmer et al., AIDS Res Hum Retroviruses, 2001, 17:1167-73). These nucleoside and nucleotide compounds are analogs of the naturally occurring deoxyribose nucleotides, however, the analogs lack the 3′-hydroxyl group on the deoxyribose sugar. As a result, when the analogs are incorporated into a growing viral DNA chain, the incoming deoxynucleotide cannot form a phosphodiester bond with the analog that is needed to extend the DNA chain. Thus, the analogs terminate viral DNA replication. Another class of reverse transcriptase inhibitors is the non-nucleoside reverse transcriptase inhibitors, such as Efavirenz, Nevirapine, Delavirdine, and Etravirine (El Safadi et al., Appl Microbiol Biotechnol, 2007, 75:723-37). They have a different mode of action than the nucleoside and nucleotide inhibitors, binding to the reverse transcriptase and interfering with its function.

The late stages of HIV replication involve processing of certain viral proteins prior to the final assembly of new virions. This late-stage processing is dependent, in part, on the activity of a viral protease. Thus, another area of focus in the development of antiretroviral drugs is protease inhibitors, such as saquinavir, ritonavir, indinavir, nelfinavir, amprenavir, lopinavir, and atazanavir (Erickson, J., 1990, Science 249:527-533; Klei et al., J Virol, 81:9525-35).

Other antiretroviral drugs target viral entry into the cell, the earliest stage of HIV infection. For HIV to enter a cell, its surface gp120 protein binds to CD4, exposing a conserved region of gp120 that binds to a CCR5 or a CXCR4 co-receptor. After gp120 binds to the co-receptor, a hydrophobic fusion peptide at the N-terminus of the gp41 envelope protein is exposed and inserted into the membrane of the cell. Entry inhibitors work by interfering with any stage of the viral entry process. For example, recombinant soluble CD4, for example, has been shown to inhibit infection of CD-4⁺ T-cells by some HIV-1 strains (Smith, D. H. et al., 1987, Science 238:1704-1707). Similarly, TNX-355 is a monoclonal antibody that binds CD4 and inhibits binding to gp120 (Kuritzkes et al., J Infect Dis, 2004, 189:286-91). BMS-806 binds to the viral envelope protein and inhibits binding to CD4 (Veazy et al., Nature 2003, 438:99-102). Co-receptor binding can be inhibited by several CCR5 inhibitors, including SCH-C and SCH-D, UK-427,857, maraviroc, vicriviroc, and an anti-CCR5 antibody (PRO-140) (Emmelkamp et al., Eur J Med Res, 2007, 12:409-17). Co-receptor binding can also be inhibited by the CXCR4 inhibitors AMD3100 and AMD070 (De Clerq, Nature Reviews Drug Discovery 2003, 2:581-87). Other compounds, such as enfuvirtide, bind to gp41 and interfere with its ability to mediate membrane fusion and entry (La Bonte et al., Nature Reviews Drug Discovery 2003, 2:345-36).

While beneficial, these antiretroviral drugs often exhibit toxic side effects such as bone marrow suppression, vomiting, and liver function abnormalities. In addition, they are not curative, probably due to the rapid appearance of drug resistant HIV mutants (Lander, B. et al., 1989, Science 243:1731-1734). Drug-resistant HIV strains develop due to the very high genetic variability of HIV. This genetic variability results from several factors, including HIV's fast replication cycle, with the generation of 10⁹ to 10¹⁰ virions per day, a high mutation rate of approximately 3×10⁻⁵ per nucleotide base per cycle of replication, and recombinogenic properties of reverse transcriptase.

To combat the development of drug resistant HIV strains, multiple drugs have been combined as part of highly active antiretroviral therapy (HAART) (El Safadi et al., Appl Microbiol Biotechnol, 2007, 75:723-37; Sharma et al., Cur Top Med Chem, 2004, 4:895-919). Currently HAART typically involves combining at least three drugs belonging to at least two classes of antiretroviral agents. As discussed above, these classes include nucleoside or nucleotide analog reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, protease inhibitors, and entry inhibitors.

Thus, although a great deal of effort is being directed to the design and testing of anti-viral drugs, the search for new and improved methods of treating viral infections, such as HIV, continues.

SUMMARY

The present disclosure provides methods of using azide-modified biomolecules, such as azide-modified fatty acids, azide-modified carbohydrates, or azide-modified isoprenoid lipids, for treating viral infections, such as HIV infections, or for labeling a protein of a virus, such as HIV, as well as pharmaceutical compositions containing an azide-modified biomolecule.

One aspect of the disclosure is directed to a method of treating a plant or an animal infected with a virus, the method comprising administering to the plant or animal an effective amount of an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid.

Another aspect of the disclosure is directed a method of inhibiting the infectivity of a virus, the method comprising contacting a cell infected with the virus with an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid in an amount effective to inhibit the infectivity of the virus.

A third aspect of the disclosure is directed to a method of producing a human immunodeficiency virus labeled with an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid, the method comprising contacting a cell infected with the human immunodeficiency virus with the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid so that the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid enters the cell and is incorporated into a protein of the virus, thereby producing the labeled virus.

Yet another aspect of the disclosure is directed to a pharmaceutical composition comprising an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid and a pharmaceutically acceptable excipient.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain embodiments of the invention, and together with the written description, serve to explain certain principles of the invention.

FIG. 1 shows a time course of azide-modified proteins in HIV-infected CEMx174 cells. CEMx174 infected cells were labeled with either (A) 15-azidopentadecanoic acid, (B) 12-azidododecanoic acid, (C) tetraacetylated N-azidoacetylgalactosamine, or (D) tetraacetylated N-azidoacetyl-D-mannosamine and were harvested at 12, 24, 72 hours, and 14 days post-infection. FIG. 1(E) shows a representative gel that was post-stained with the total protein stain: SYPRO® Ruby protein stain (Sigma-Aldrich, St. Louis, Mo.).

FIG. 2 shows gel electrophoresis of azide-modified proteins from HIV produced from chronically infected CEMx174 cells. FIG. 2(A) shows viral proteins tagged with tetraacetylated N-azidoacetyl-D-mannosamine (Man), tetraacetylated N-azidoacetylgalactosamine (GalNaz), 15-azidopentadecanoic acid (Palmitic), 12-azidododecanoic acid (Myristic) and labeled with TAMRA. FIG. 2(B) shows a total protein stain using SYPRO® Ruby protein stain (Sigma-Aldrich, St. Louis, Mo.).

FIG. 3 shows the results of a luciferase reporter assay (Applied Biosytems luciferase reagent) to measure the infectivity of unlabeled HIV (CONTROL) or HIV labeled with 15-azidopentadecanoic acid (PALM), 12-azidododecanoic acid (MYR), tetraacetylated N-azidoacetyl-D-mannosamine (MAN), or tetraacetylated N-azidoacetylgalactosamine (GAL).

FIG. 4 shows the results of a luciferase reporter assay (Promega luciferase reagent) to measure the infectivity of unlabeled HIV (CONTROL) or HIV labeled with 15-azidopentadecanoic acid (PALM), 12-azidododecanoic acid (MYR), tetraacetylated N-azidoacetyl-D-mannosamine (MAN), or tetraacetylated N-azidoacetylgalactosamine (GAL).

DEFINITIONS

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention is related. In order that the present invention may be more readily understood, certain terms are first defined. Additional definitions are set forth throughout the detailed description. In case of conflict, the present specification, including definitions, will control.

As used herein, “azide-modified fatty acid” refers to a fatty acid that comprises an azido group and has the following formula, R—N₃ where R comprises a hydrocarbon chain with at least one carboxylic acid functional group, which is usually, although not necessarily, at a terminal position.

As used herein, “azide-modified carbohydrate” refers to a carbohydrate that comprises an azido group and has the following formula, R—N₃ where R is a carbohydrate.

As used herein, “azide-modified isoprenoid lipid” refers to an isoprene-containing lipid, or derivative thereof. The azide-modified isoprenoid comprises an azido group and has the following formula, R—N₃ where R is an isoprene-containing lipid, such as the C₁₅ farnesyl isoprenoid lipid or the C₂₀ geranylgeranyl isoprenoid lipid, or a derivative thereof, including, but not limited to, an azido farnesyl diphosphate, an azido farnesyl alcohol, an azido geranylgeranyl diphosphate, or an azido geranylgeranyl alcohol.

As used herein, “animal virus” refers to a virus that infects a non-human, animal cell. In certain instances, a virus that infects non-human animal cells is also capable of infecting human cells.

As used herein, “biomolecule,” refers to proteins, peptides, amino acids, glycoproteins, nucleic acids, nucleotides, nucleosides, oligonucleotides, sugars, oligosaccharides, lipids, hormones, proteoglycans, carbohydrates, polypeptides, polynucleotides, polysaccharides, which having characteristics typical of molecules found in living organisms and may be naturally occurring or may be artificial (not found in nature and not identical to a molecule found in nature).

As used herein, “click chemistry,” refers to the copper(I)-catalyzed variant of the Huisgen cycloaddition or the 1,3-dipolar cycloaddition between an azide and a terminal alkyne to form a 1,2,4-triazole. Such chemical reactions can use, but are not limited to, simple heteroatomic organic reactants and are reliable, selective, stereospecific, and exothermic.

As used herein, “cycloaddition” refers to a chemical reaction in which two or more π (pi)-electron systems (e.g., unsaturated molecules or unsaturated parts of the same molecule) combine to form a cyclic product in which there is a net reduction of the bond multiplicity. In a cycloaddition, the π (pi) electrons are used to form new π (pi) bonds. The product of a cycloaddition is called an “adduct” or “cycloadduct”. Different types of cycloadditions are known in the art including, but not limited to, [3+2]cycloadditions and Diels-Alder reactions. [3+2]cycloadditions, which are also called 1,3-dipolar cycloadditions, occur between a 1,3-dipole and a dipolarophile and are typically used for the construction of five-membered heterocyclic rings. The term “[3+2]cycloaddition” also encompasses “copperless” [3+2]cycloadditions between azides and cyclooctynes and difluorocyclooctynes described by Bertozzi et al. J. Am. Chem. Soc., 2004, 126:15046-15047.

As used herein, “DNA virus” refers to a virus that has deoxyribonucleic acid (DNA) as its genetic material. DNA viruses are usually double stranded but may also be single stranded.

As used herein, “glycoprotein” refers to a protein that has been glycosylated and those that have been enzymatically modified, in vivo or in vitro, to comprise a carbohydrate group.

As used herein, “HIV” and “human immunodeficiency virus” refer to human immunodeficiency virus 1 and 2 (HIV-1 and HIV-2).

As used herein, “human virus” refers to a virus that infects human cells. In certain instances, a virus that infects human cells is also capable of infecting cells of other non-human, animal cells.

As used herein, “infectivity” refers to the ability of a virus to enter a cell.

As used herein, “plant virus” refers to a virus that infects plant cells.

As used herein, “pharmaceutically acceptable excipient” includes solvents, dispersion media, diluents, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, etc., that are compatible with pharmaceutical administration. Use of these agents for pharmaceutically active substances is well known in the art.

As used herein, “protein” and “polypeptide” are used in a generic sense to include polymers of amino acid residues of any length. The term “peptide” is used herein to refer to polypeptides having less than 100 amino acid residues, typically less than 10 amino acid residues. The terms apply to amino acid polymers in which one or more amino acid residues are an artificial chemical analogue of a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers.

As used herein, “reporter molecule” refers to any moiety capable of being attached to a modified post translationally modified protein of the present invention, and detected either directly or indirectly. Reporter molecules include, without limitation, a chromophore, a fluorophore, a fluorescent protein, a phosphorescent dye, a tandem dye, a particle, a hapten, an enzyme and a radioisotope. Preferred reporter molecules include fluorophores, fluorescent proteins, haptens, and enzymes.

As used herein, “RNA virus” refers to a virus that has ribonucleic acid (RNA) as its genetic material. RNA viruses are usually single stranded but may also be double stranded.

As used herein, the term “subject” is intended to include human and non-human animals. Subjects may include a human patient having a viral infection, including, but not limited to, an HIV infection. The term “non-human animals” of the invention includes all vertebrates, such as non-human primates, sheep, dogs, cows, chickens, amphibians, reptiles, etc.

As used herein, “treatment” or “treating” refers to a therapeutic or preventative measure. The treatment may be administered to a subject having a medical disorder or who ultimately may acquire the disorder, in order to prevent, cure, delay, reduce the severity of, and/or ameliorate one or more symptoms of a disorder or recurring disorder, or in order to prolong the survival of a subject beyond that expected in the absence of such treatment.

As used herein, a “therapeutically effective amount” or “effective amount” means the amount of a compound that, when administered to a mammal or other subject for treating a disease, is sufficient to effect such treatment for the disease. The “effective amount” will vary depending on the compound, the disease and its severity and the age, weight, etc., of the subject to be treated.

It must be noted that, as used in this specification and the appended claims, the singular form “a”, “an” and “the” include plural referents unless the context dictates otherwise. Thus, for example, reference to “a virus” includes a plurality of viruses unless the context dictates otherwise.

While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

DETAILED DESCRIPTION

The present disclosure concerns the use of azide-modified biomolecules, such as fatty acids or carbohydrates, for treating viral infections, as well as pharmaceutical compositions containing an azide-modified biomolecule. Azide-modified fatty acids, azide-modified carbohydrates, and azide-modified isoprenoid lipids have been previously described as useful reagents for labeling and detecting proteins of interest as part of a click chemistry reaction involving a copper (I)-catalyzed cycloaddition reaction between an azide and an alkyne. See CLICK-IT® metabolic labeling reagents for proteins (Invitrogen, Carlsbad, Calif.); see also, U.S. Patent Application Publication No. 2007/0249014 and U.S. Patent Application Publication No. 20050222427, which disclosures are hereby incorporated by reference in its entirety. Applicants, however, have unexpectedly discovered that these azide-modified biomolecules have anti-viral activity and can be used to treat viral infections. It was surprisingly discovered that these azide-modified biomolecules profoundly affect viral infectivity and that labeling viruses with these azide-modified biomolecules inhibited viral entry into host cells. Without intending to be bound by any theory, it appears that post-translational modification of viral proteins with an azido-modified biomolecule at sites normally occupied by unmodified biomolecules, such as saturated fatty acids (e.g., myristic acid and palmitic acid), may result in the inhibition of infectivity of the virus in a manner similar to the absence of these biomolecules at these sites.

Click Chemistry

Azides and terminal or internal alkynes can undergo a 1,3-dipolar cycloaddition (Huisgen cycloaddition) reaction to give a 1,2,3-triazole. However, this reaction requires long reaction times and elevated temperatures. Alternatively, azides and terminal alkynes can undergo Copper(I)-catalyzed Azide-Alkyne Cycloaddition (CuAAC) at room temperature. Such copper(I)-catalyzed azide-alkyne cycloadditions, also known as click chemistry, is a variant of the Huisgen 1,3-dipolar cycloaddition wherein organic azides and terminal alkynes react to give 1,4-regioisomers of 1,2,3-triazoles. Examples of click chemistry reactions are described by Sharpless et al. (U.S. Patent Application Publication No. 20050222427, PCT/US03/17311; Lewis W G, et al., Angewandte Chemie-Int'l Ed. 41 (6): 1053; method reviewed in Kolb, H. C., et al., Angew. Chem. Inst. Ed. 2001, 40:2004-2021), which developed reagents that react with each other in high yield and with few side reactions in a heteroatom linkage (as opposed to carbon-carbon bonds) in order to create libraries of chemical compounds.

Click chemistry has been used to label and detect proteins of interest. For example, the CLICK-IT® (Invitrogen, Carlsbad, Calif.) reaction is a two-step labeling technique involving the incorporation of a modified metabolic precursor, such as an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid, into proteins as a chemical “handle” followed by the chemoselective ligation (or “click” reaction) between an azide and an alkyne. In the click reaction, the modified protein is detected with a corresponding azide- or alkyne-containing dye or hapten. The CLICK-IT® metabolic labeling reagents have been used to monitor post translational modifications of proteins, such as acylation, glycosylation, and prenylation, and include 1) azide-modified fatty acids, such as CLICK-IT® palmitic acid azide (i.e., 15-azidopentadecanoic acid) and CLICK-IT® myristic acid azide (i.e., 12-azidododecanoic acid), for labeling palmitoylated and myristoylated proteins, respectively; 2) azide-modified carbohydrates, including CLICK-IT® GalNAz (tetraacetylated N-azidoacetylgalactosamine) for labeling O-linked glycoproteins, CLICK-IT® ManNAz (tetraacetylated N-azidoacetyl-D-mannosamine) for labeling sialic acid modified glycoproteins, and CLICK-IT® GlcNAz (tetraacetylated N-azidoacetylglucosamine) for labeling O-GlcNAz-modified glycoproteins; and 3) azide-modified isoprenoid lipids, such as CLICK-IT® farnesyl alcohol azide and CLICK-IT® geranylgeranyl alcohol azide. As noted above, Applicants, have unexpectedly found that these azide-modified biomolecules have anti-viral activity and can be used to treat viral infections.

Glycosylation

Glycosylation is an enzymatic process in which carbohydrates are attached to proteins, lipids, or other organic molecules in a cell. Glycoproteins are biomolecules composed of proteins covalently linked to carbohydrates. Certain post-translational modifications append a sugar moiety (carbohydrate) onto a protein, thereby forming a glycoprotein. The common monosaccharides found in glycoproteins include, but are not limited to, glucose, galactose, mannose, fucose, xylose, N-acetylgalactosamine (GalNAc), N-acetylglucosamine (GlcNAc) and N-acetylneuraminic acid (NANA, also known as sialic acid). N-acetyl-D-mannosamine (ManNAc) is a precursor of the neuraminic acids, including NANA. Two of the same or different monosaccharides can join together to form a disaccharide. The addition of more monosaccharides results in the formation of oligosaccharides of increasing length. In addition, the sugar moiety can be a glycosyl group.

In glycoproteins the carbohydrates can be linked to the protein component by either N-glycosylation or O-glycosylation. N-glycosylation commonly occurs through a nitrogen on an asparagine or arginine side chain, forming an N-glycosidic linkage via an amide group. O-glycosylation commonly occurs at the hydroxy oxygen of hydroxylysine, hydroxyproline, serine, tyrosine or threonine side chains, forming an O-glycosidic linkage. GalNAc and GlcNAc are both O-linked carbohydrates. Sialic acid is found on both N- and O-linked carbohydrates.

Protein glycosylation is one of the most abundant post-translational modifications and plays a fundamental role in the control of biological systems. For example, glycosylation influences protein folding and can help to stabilize proteins and prevent their degradation. Glycosylation also can affect a protein's ability to bind to other molecules and mediate intra- or inter-cellular signaling pathways. For example, carbohydrate modifications are important for host-pathogen interactions, inflammation, development, and malignancy (Varki, A. Glycobiology 1993, 3, 97-130; Lasky, L. A. Annu. Rev. Biochem. 1995, 64, 113-139. (c) Capila, I.; Linhardt, R. J. Angew. Chem., Int. Ed. 2002, 41, 391-412; Rudd, P. M.; Elliott, T.; Cresswell, P.; Wilson, I. A.; Dwek, R. A. Science 2001, 291, 2370-2376). One such covalent modification is O-GlcNAc glycosylation, which is the covalent modification of serine and threonine residues by D-N-acetylglucosamine (Wells, L.; Vosseller, K.; Hart, G. W. Science 2001, 291, 2376-2378; Zachara, N. E.; Hart, G. W. Chem. Rev. 2002, 102, 431). The O-GlcNAc modification is found in all higher eukaryotic organisms from C. elegans to man and has been shown to be ubiquitous, inducible and highly dynamic, suggesting a regulatory role analogous to phosphorylation.

Fatty Acid Acylation

Fatty acid acylation is an enzymatic process in which fatty acids are attached to proteins in a cell. This process can affect a protein's function as well as its cellular location and is common to proteins of both cellular and viral origin (Towler et al., Proc Natl Acad Sci USA 1986, 83:2812-16). Myristic acid and palmitic acid are the two most common fatty acids that are attached to proteins (Olson et al., J Biol Chem 261(5):2458-66). Generally myristic acid is attached to soluble and membrane proteins via an amide linkage to an amino terminal glycine exposed during removal of an N-methionine residue, although it can also attach to other amino acids. Myristoylation can also occur post-translationally, for example, when a protease cleaves a polypeptide and exposes a glycine residue. Palmitic acid is attached to membrane proteins via an ester or thioester linkage. Myristoylation and palmitoylation appear to play a significant role in subcellular trafficking of proteins between membrane compartments, as well as in modulating protein-protein interactions.

Fatty acids have two distinct regions, a long hydrophobic, hydrocarbon chain and a carboxylic acid group, which is generally ionized in solution (COO—), extremely hydrophilic and readily forms esters and amides. Natural fatty acids commonly have a chain of four to 28 carbons (usually unbranched and even numbered) and may be saturated or unsaturated. Saturated fatty acids contain no double bonds in the hydrocarbon chain and include lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid. Unsaturated fatty acids contain at least one double bond in the hydrocarbon chain and include myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, linoleic acid, α-linoleic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, and docosahexaenoic acid.

Prenylation

Protein prenylation involves the attachment of an isoprenoid lipid, such as a farnesyl or a geranyl-geranyl moiety, to a C-terminal cysteine(s) of the target protein (McTaggert, Cell Mol Life Sci 2006, 63:255-67). These reactions are catalysed by farnesyltransferase, geranylgeranyltransferase, and Rab geranylgeranyltransferase. (Magee and Seabra, Biochem J 2003, 376:e3-4). Due to the hydrophobic nature of the isoprenoid lipid, most prenylated proteins are associated with a membrane. Most farnesylated proteins are involved in cellular signaling where membrane association is important for function. Isoprenoid lipids are also important for mediating protein-protein binding through specialized prenyl-binding domains.

Post Translational Modifications in Viruses

Many viral proteins are extensively modified with post translational modifications, including, but not limited to glycosylation, acylation, and prenylation. In many instances, these post translational modifications are required for the virus to infect a host cell and/or evade the immune system. Post translational modifications are of particular importance in virology because, in general, viral genomes are small and thus there is heightened pressure for coding frugality. By taking advantage of a host's post translational machinery, viruses can exploit multiple pathways and function with minimal genomes, as a single post translational modification can alter a protein's function or cellular location.

For example, in HIV and Simian Immunodeficiency Viruses (SIV), glycosylation plays an important role during multiple stages of the infectivity cycle. During infection, viral glycoproteins influence the binding of viral proteins gp120 and gp41 to host cell CD4 receptor and CXCR4 and CCR5 co-receptors (Chen et al., Virus Res 2001, 79:91-101). Glycosylation is responsible for the proper folding and processing of gp160 (the precursor to gp120 and gp41 (Land et al., Biochimie 2001, 83: 783-90) and can enhance the interactions of HIV and SIV with different cell types, including dendritic cells (Geijtenbeek et al., Curr Top Microbiol Immunol 2003, 276:31-54). The normal role of gp120 in HIV biology is to initiate viral binding to cells via CD4 receptor and CXCR4 and CCR5 co-receptors expressed on the target cell. When gp120 engages CD4, conformational changes occur in gp120 that expose co-receptor binding sites and trigger conformational changes in gp41. The conformational changes in gp41, in turn, expose a fusion peptide in gp41, that mediates fusion between the viral envelope and the target cell (Chen et al., Virus Res 2001, 79:91-101). The change of one carbohydrate at a single residue (N197) in gp120 completely changes viral tropism from CD4 tropic to CD4 independent (Kolchinksy et al., J Virol 2001, 75:3435-43). Changing the overall ratios of high mannose in comparison to complex type carbohydrates (sialic acid containing) present in gp120 affects the degree of viral binding to target cells (Fenouillet et al., J Gen Virol 1991, 1919-26). Following infection, glycosylation is required for cleavage of the envelope precursor protein (gp160) into gp120 and gp41. Upon release of the virus from an infected cell, glycosylation is also important for immune evasion as changes in envelope glycosylation significantly alter humoral immune responses to virus (Kwong et al., Nature 2002, 420:678-82; Shi et al., J Gen Virol 2005, 86:3385-96).

The acylation of viral proteins is also important to HIV biology. HIV budding is a complex process involving the coordination of many cellular and viral proteins (Resh Trends Microbiol 2001, 9:57; Freed, J Virol 2002, 76:4679-87). HIV budding is directed to an area of the plasma membrane enriched in membrane rafts (Lindwasser et al., J Virol 2001, 75:7913-24; Nguyen et al., J Virol 2000, 74:3264-72; Ono et al., Proc Natl Acad Sci USA 2001, 98:13925-30; Hermida-Matsumoto et al., J Virol 2000, 74:8670-79), previously called lipid rafts (Pike et al., J Lipid Res 2006, 47:1597-98) by myristoylation of the N-terminal glycine of the capsid protein polyprotein precursor (pr55 gag) (Lindwasser et al., J Virol 2001, 75:7913-24; Nguyen et al., J Virol 2000, 74:3264-72; Ono et al., Proc Natl Acad Sci USA 2001, 98:13925-30). The gp120 protein is directed to membrane rafts by palmitoylation (Yang et al., Proc Natl Acad Sci USA 1995, 92:9871-75). Membrane rafts play an important role in several cellular processes including endocytosis, vesicle transport, cholesterol sorting, apoptosis, and signaling through the T cell receptor (Jordan et al., J Immunol 2003, 171:78-87; Viola et al., Apmis 1999, 107:615-23; Viola et al., Science 1999, 283:680-82; Bezombes et al., Curr Med Chem Anti-Canc Agents 2002, 3:263-70; Kabouridis et al., Eur J Immunol 2000, 30:954-63). Direction of HIV proteins to these regions may allow the virions to more efficiently hijack these pathways, thus potentially explaining the complex pathogenicity associated with disease progression in AIDS. In fact, the removal of cholesterol, an important membrane raft component, from HIV particles results in inactivation by at least two mechanisms, a loss of the ability to fuse to the target cell and the loss of virion integrity resulting in permeabilization of the virus (Guyader et al, J Virol 2002, 76:10356-64; Campbell et al., J Virol 2004, 78:10556-65; Viard et al., J Virol 2002, 76:11584-595; Campbell et al., Aids 2002, 16:2253-61; Liao et al, AIDS Res Hum Retroviruses 2003, 19:675-87; Graham et al., J Virol 2003, 77:8237-48).

Viruses can also use the host cell machinery to modify viral proteins by adding isoprenoid lipids, such as the farnesyl and geranylgeranyl groups. For example, prenylation plays an important role in the life cycle of the hepatitis delta virus (HDV), the etiologic agent of acute and chronic liver disease associated with hepatitis B virus. (Einav and Glenn, J Antimicrobial Chemotherapy 2003, 52:883-86). One of the HDV proteins, the large delta antigen (LHDAg), is critical for viral assembly and undergoes farnesylation in both in vitro translation systems and in intact cells. (Einav and Glenn, J Antimicrobial Chemotherapy 2003, 52:883-86). Inhibiting prenylation by using farnesyltransferase inhibitors prevents HDV assembly and clears HDV viremia in a mouse model of HDV, thus underscoring the importance of prenylation in the life cycle of certain viruses. (Einav and Glenn, J Antimicrobial Chemotherapy 2003, 52:883-86).

Similar to HIV, SIV, and HDV, other viruses rely on post translational modifications of viral proteins to mediate entry into host cells and/or to evade the host immune system. Thus, the azide-modified fatty acids, azide-modified carbohydrates, and azide-modified isoprenoid lipids described herein are expected to have a broad range of anti-viral activity (such as modulating activity by inhibiting or preventing reverse transcription of the HIV viral genome, late-stage processing of certain viral proteins prior to final assembly of new virons, or viral entry into the cell) and can be used to treat a wide variety of viral infections.

Methods of Use

1. Method of Treating a Viral Infection

The present disclosure provides a method of treating a plant or an animal infected with a virus, the method comprising administering to the plant or animal an effective amount of an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid. In one embodiment, the azide-modified fatty acid is a saturated fatty acid, such as 15-azidopentadecanoic acid or 12-azidododecanoic acid. In another embodiment, the azide-modified carbohydrate is an N-linked carbohydrate or an O-linked carbohydrate. In yet another embodiment, the azide-modified carbohydrate is N-azidoacetylgalactosamine, N-azidoacetyl-D-mannosamine, or N-azidoacetylglucosamine. The azide-modified carbohydrate optionally comprises a moiety that facilitates entry into the cell including, but not limited to, a tetraacetyl moiety. Thus, in another embodiment, the azide-modified carbohydrate is tetraacetylated N-azidoacetylgalactosamine, tetraacetylated N-azidoacetyl-D-mannosamine, or tetraacetylated N-azidoacetylglucosamine. In another embodiment, the isoprenoid lipid comprises a farnesyl group or a geranylgeranyl group and includes, but is not limited to, an azido farnesyl diphosphate, an azido farnesyl alcohol, an azido geranylgeranyl diphosphate, or an azido geranylgeranyl alcohol.

The virus may be a plant virus, an animal virus, and/or a human virus. In certain embodiments, the animal is a human and the virus is a human virus, such as an adenovirus, an astrovirus, a hepadnavirus, a herpesvirus, a papovavirus, a poxvirus, an arenavirus, a bunyavirus, a calcivirus, a coronavirus, a filovirus, a flavivirus, an orthomyxovirus, a paramyxovirus, a picornavirus, a reovirus, a retrovirus, a rhabdovirus, or a togavirus. In one embodiment, the animal is a human and the virus is a human immunodeficiency virus. Preferably the human immunodeficiency virus is HIV-1.

Whether the azide-modified fatty acid, azide-modified carbohydrate, or azide-modified isoprenoid lipid is effective to treat a viral infection can be determined using any of a variety of assays known in the art. For example, existing animal models or in vitro models of viral infection can be used to determine whether a given compound is effective to reduce viral load. For HIV, by way of example, the in vitro, luciferase reporter assay described in Example 2, can be used to measure the efficacy of an azide-modified compound. In a human subject, the compound's efficacy can be determined by measuring viral load and/or measuring one or more symptoms of a viral infection. Viral load can be measured by measuring the titer or level of virus in serum. These methods include, but are not limited to, a quantitative polymerase chain reaction (PCR) and a branched DNA (bDNA) test.

2. Method of Inhibiting Infectivity of a Virus

Also provided is a method of inhibiting the infectivity of a virus, the method comprising contacting a cell infected with the virus with an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid in an amount effective to inhibit the infectivity of the virus. In one embodiment, the azide-modified fatty acid is a saturated fatty acid, such as 15-azidopentadecanoic acid or 12-azidododecanoic acid. In another embodiment, the azide-modified carbohydrate is an N-linked carbohydrate or an O-linked carbohydrate. In yet another embodiment, the azide-modified carbohydrate is N-azidoacetylgalactosamine, N-azidoacetyl-D-mannosamine, or N-azidoacetylglucosamine. The azide-modified carbohydrate optionally comprises a moiety that facilitates entry into the cell including, but not limited to, a tetraacetyl moiety. Thus, in another embodiment, the azide-modified carbohydrate is tetraacetylated N-azidoacetylgalactosamine, tetraacetylated N-azidoacetyl-D-mannosamine, or tetraacetylated N-azidoacetylglucosamine. In another embodiment, the isoprenoid lipid comprises a farnesyl group or a geranylgeranyl group and includes, but is not limited to, an azido farnesyl diphosphate, an azido farnesyl alcohol, an azido geranylgeranyl diphosphate, or an azido geranylgeranyl alcohol.

The virus may be a plant virus, an animal virus, and/or a human virus. In certain embodiments, the cell is a human cell and the virus is a human virus, such as an adenovirus, an astrovirus, a hepadnavirus, a herpesvirus, a papovavirus, a poxvirus, an arenavirus, a bunyavirus, a calcivirus, a coronavirus, a filovirus, a flavivirus, an orthomyxovirus, a paramyxovirus, a picornavirus, a reovirus, a retrovirus, a rhabdovirus, or a togavirus. In one embodiment, the animal is a human and the virus is a human immunodeficiency virus. Preferably the human immunodeficiency virus is HIV-1.

Whether the azide-modified fatty acid, azide-modified carbohydrate, or azide-modified isoprenoid lipid is effective to inhibit the infectivity of a virus can be determined using any of a variety of assays known in the art, including a reporter gene assay, such as the luciferase assay described in Example 2.

3. Method of Labeling a Viral Protein

An azide-modified fatty acid can also be used to label viral proteins that are modified with lipids by post-translational acylation including, but not limited to, palmitoylation and myristoylation. In such post-translational modifications, an azide-modified fatty acid is used to label a viral protein. If desired, the azide labeled viral protein can be coupled to an alkyne labeled reporter molecule using a click chemistry reaction to permit detection of the azide labeled viral protein.

Similarly, an azide-modified carbohydrate can be used to label viral proteins that are modified with carbohydrates by post-translational glycosylation including, but not limited to, N-linked glycosylation and O-linked glycosylation. In such post-translational modifications, an azide-modified carbohydrate is used to label a viral protein. If desired, the azide labeled viral protein can be coupled to an alkyne labeled reporter molecule using click chemistry to permit the detection of the azide labeled viral protein.

An azide-modified isoprenoid lipid can likewise be used to label viral proteins that are modified with lipids by post-translational prenylation including, but not limited to, farnesylation and geranylgeranylation. In such post-translational modifications, an azide-modified isoprenoid lipid is used to label a viral protein. If desired, the azide labeled viral protein can be coupled to an alkyne labeled reporter molecule using a click chemistry reaction to permit detection of the azide labeled viral protein.

The azide labeled virus can used to track viral infectivity in vivo whereby the virus labeled with an azide-modified carbohydrate, azide-modified fatty acid, or azide-modified isoprenoid lipid is used to infect cultured cells or laboratory animals. Cells can be infected over a time course then fixed, permeabilized, and click-labeled with a fluorescent alkyne dye. The intracellular location (or transport over a time course) of the fluorescent viral particles can be visualized, for example, by microscopy. Similarly, treatment of small animals with azide-labeled virus can be performed and used to track virus bioavailability in different tissues including detection of the virus in circulating white blood cells by flow cytometry and cell/tissue section microscopy

Thus, another aspect of the disclosure is directed to a method of producing a human immunodeficiency virus labeled with an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid, the method comprising contacting a cell infected with the human immunodeficiency virus with the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid so that the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid enters the cell and is incorporated into a protein of the virus, thereby producing the labeled virus. In one embodiment, the azide-modified fatty acid is a saturated fatty acid, such as 15-azidopentadecanoic acid or 12-azidododecanoic acid. In another embodiment, the azide-modified carbohydrate is an N-linked carbohydrate or an O-linked carbohydrate. In yet another embodiment, the azide-modified carbohydrate is N-azidoacetylgalactosamine, N-azidoacetyl-D-mannosamine, or N-azidoacetylglucosamine. In another embodiment, the isoprenoid lipid comprises a farnesyl group or a geranylgeranyl group and includes, but is not limited to, an azido farnesyl diphosphate, an azido farnesyl alcohol, an azido geranylgeranyl diphosphate, or an azido geranylgeranyl alcohol. The azide-modified carbohydrate optionally comprises a moiety that facilitates entry into the cell including, but not limited to, a tetraacetyl moiety. Thus, in another embodiment, the azide-modified carbohydrate is tetraacetylated N-azidoacetylgalactosamine, tetraacetylated N-azidoacetyl-D-mannosamine, or tetraacetylated N-azidoacetylglucosamine. In certain embodiments, the cell is a human cell.

Viruses

The azide-modified fatty acids, azide-modified carbohydrates, or azide-modified isoprenoid lipids preferably target post translational modifications common to most viruses and thus represent a new class of anti-viral agents with potential for anti-viral activity against a broad spectrum of viruses. In principle, these compounds may be used to treat a plant or an animal infected with any virus. In some embodiments, the virus is a plant virus. In other embodiments, the virus is an animal virus. In yet other embodiments, the virus is a human virus. In one embodiment, the virus is one that infects a non-human mammal, such as a mammalian livestock animal, including, but not limited to, a cow, a horse, a pig, a goat, or a sheep.

In other embodiments, the virus is a DNA virus. DNA viruses include, but are not limited to a virus belonging to one of the following families: adenovirus, astrovirus, hepadnavirus, herpesvirus, papovavirus, and poxvirus. In other embodiments, the virus is an RNA virus. RNA viruses include but are not limited to a virus belonging to one the following families: arenavirus, bunyavirus, calcivirus, coronavirus, filovirus, flavivirus, orthomyxovirus, paramyxovirus, picornavirus, reovirus, retrovirus, rhabdovirus, and togavirus.

1. Animal Viruses

In methods directed to treating a viral infection or inhibiting viral infectivity in a non-human animal, the animal virus is preferably selected from a picornavirus, such as a bovine enterovirus, a porcine enterovirus B, a foot-and-mouth disease virus, an equine rhinitis A virus, a bovine rhinitis B virus, a ljungan virus, equine rhinitis B virus, an aichi virus, a bovine kobuvirus, a porcine teschovirus, a porcine sapelovirus, a simian sapelovirus, an avian sapelovirus, an avian encephalomyelitis virus, a duck hepatitis A virus, or a simian enterovirus A; a pestivirus, such as border disease virus, a bovine virus diarrhea, or a classical swine fever virus; an arterivirus, such as an equine arteritis virus, a porcine reproductive and respiratory syndrome virus, a lactate dehydrogenase elevating virus, or a simian haemorrhagic fever virus; a coronavirus, such as a bovine coronavirus, a porcine coronavirus, a feline coronavirus, or a canine coronavirus; a paramyxovirus, such as a hendra virus, a nipah virus, a canine distemper virus, a rinderpest virus, a Newcastle disease virus, and a bovine respiratory syncytial virus; an orthomyxovirus, such as an influenza A virus, an influenza B virus, or an influenza C virus; a reovirus, such as a bluetongue virus; a porcine circovirus, a herpesvirus, such as a pseudorabies virus or a bovine herpesvirus 1; an asfarvirus, such as an African swine fever virus; a retrovirus, such as a simian immunodeficiency virus, a feline immunodeficiency virus, a bovine immunodeficiency virus, a bovine leukemia virus, a feline leukemia virus, a Jaagsiekte sheep retrovirus, or a caprine arthritis encephalitis virus; a flavivirus, such as a yellow fever virus, a West Nile virus, a dengue fever virus, a tick borne encephalitis virus, or a bovine viral diarrhea; or a rhabdovirus, such as a rabies virus.

2. Human Viruses

In methods directed to treating a viral infection or inhibiting viral infectivity in a human, the human virus is preferably selected from an adenovirus, an astrovirus, a hepadnavirus, a herpesvirus, a papovavirus, a poxvirus, an arenavirus, a bunyavirus, a calcivirus, a coronavirus, a filovirus, a flavivirus, an orthomyxovirus, a paramyxovirus, a picornavirus, a reovirus, a retrovirus, a rhabdovirus, or a togavirus.

In preferred embodiments, the adenovirus includes, but is not limited to, a human adenovirus. In preferred embodiments, the astrovirus includes, but is not limited to, a mamastrovirus. In preferred embodiments, the hepadnavirus includes, but is not limited to, the hepatitis B virus. In preferred embodiments, the herpesvirus includes, but is not limited to, a herpes simplex virus type I, a herpes simplex virus type 2, a human cytomegalovirus, an Epstein-Barr virus, a varicella zoster virus, a roseolovirus, and a Kaposi's sarcoma-associated herpesvirus. In preferred embodiments, the papovavirus includes, but is not limited to, human papilloma virus and a human polyoma virus. In preferred embodiments, the poxvirus includes, but is not limited to, a variola virus, a vaccinia virus, a cowpox virus, a monkeypox virus, a smallpox virus, a pseudocowpox virus, a papular stomatitis virus, a tanapox virus, a yaba monkey tumor virus, and a molluscum contagiosum virus. In preferred embodiments, the arenavirus includes, but is not limited to lymphocytic choriomeningitis virus, a lassa virus, a machupo virus, and a junin virus. In preferred embodiments, the bunyavirus includes, but is not limited to, a hanta virus, a nairovirus, an orthobunyavirus, and a phlebovirus. In preferred embodiments, the calcivirus includes, but is not limited to, a vesivirus, a norovirus, such as the Norwalk virus and a sapovirus. In preferred embodiments, the coronavirus includes, but is not limited to, a human coronavirus (etiologic agent of sever acute respiratory syndrome (SARS)). In preferred embodiments, the filovirus includes, but is not limited to, an Ebola virus and a Marburg virus. In preferred embodiments, the flavivirus includes, but is not limited to, a yellow fever virus, a West Nile virus, a dengue fever virus, a hepatitis C virus, a tick borne encephalitis virus, a Japanese encephalitis virus, a Murray Valley encephalitis virus, a St. Louis encephalitis virus, a Russian spring-summer encephalitis virus, a Omsk hemorrhagic fever virus, a bovine viral diarrhea virus, a Kyasanus Forest disease virus, and a Powassan encephalitis virus. In preferred embodiments, the orthomyxovirus includes, but is not limited to, influenza virus type A, influenza virus type B, and influenza virus type C. In preferred embodiments, the paramyxovirus includes, but is not limited to, a parainfluenza virus, a rubula virus (mumps), a morbillivirus (measles), a pneumovirus, such as a human respiratory syncytial virus, and a subacute sclerosing panencephalitis virus. In preferred embodiments, the picornavirus includes, but is not limited to, a poliovirus, a rhinovirus, a coxsackievirus A, a coxsackievirus B, a hepatitis A virus, an echovirus, and an eneterovirus. In preferred embodiments, the reovirus includes, but is not limited to, a Colorado tick fever virus and a rotavirus. In preferred embodiments, the retrovirus includes, but is not limited to, a lentivirus, such as a human immunodeficiency virus, and a human T-lymphotrophic virus (HTLV). In preferred embodiments, the rhabdovirus includes, but is not limited to, a lyssavirus, such as the rabies virus, the vesicular stomatitis virus and the infectious hematopoietic necrosis virus. In preferred embodiments, the togavirus includes, but is not limited to, an alphavirus, such as a Ross river virus, an O'nyong'nyong virus, a Sindbis virus, a Venezuelan equine encephalitis virus, an Eastern equine encephalitis virus, and a Western equine encephalitis virus, and a rubella virus.

3. Plant Viruses

In methods directed to treating a viral infection or inhibiting viral infectivity in a plant, the plant virus is selected from an alfamovirus, an allexivirus, an alphacryptovirus, an anulavirus, an apscaviroid, an aureusvirus, an avenavirus, an aysunviroid, a badnavirus, a begomovirus, a benyvirus, a betacryptovirus, a betaflexiviridae, a bromovirus, a bymovirus, a capillovirus, a carlavirus, a carmovirus, a caulimovirus, a cavemovirus, a cheravirus, a closterovirus, a cocadviroid, a coleviroid, a comovirus, a crinivirus, a cucumovirus, a curtovirus, a cytorhabdovirus, a dianthovirus, an enamovirus, an umbravirus & B-type satellite virus, a fabavirus, a fijivirus, a furovirus, a hordeivirus, a hostuviroid, an idaeovirus, an ilarvirus, an ipomovirus, a luteovirus, a machlomovirus, a macluravirus, a marafivirus, a mastrevirus, a nanovirus, a necrovirus, a nepovirus, a nucleorhabdovirus, an oleavirus, an ophiovirus, an oryzavirus, a panicovirus, a pecluvirus, a petuvirus, a phytoreovirus, a polerovirus, a pomovirus, a pospiviroid, a potexvirus, a potyvirus, a reovirus, a rhabdovirus, a rymovirus, a sadwavirus, a SbCMV-like virus, a sequivirus, a sobemovirus, a tenuivirus, a TNsatV-like satellite virus, a tobamovirus, a topocuvirus, a tospovirus, a trichovirus, a tritimovirus, a tungrovirus, a tymovirus, an umbravirus, a varicosavirus, a vitivirus, or a waikavirus.

Azide-Modified Biomolecules

The azide-modified biomolecules described herein represent a new class of anti-viral agents. In certain embodiments, the azide-modified biomolecule is a carbohydrate or a pharmaceutically acceptable derivative or prodrug thereof. The carbohydrate can be selected from a wide variety of carbohydrates commercially available and/or widely known to those skilled in the art. In preferred embodiments, the carbohydrate is selected to prevent, inhibit and/or retard viral infection of cells. Preferably the carbohydrate is naturally occurring. It is appreciated that the azide-containing carbohydrate, whether naturally occurring or not, may be modified, for example, by short chain alkylation such as methylation or acetylation, esterification, as well as other derivitisations that maintain antiviral activity.

In one embodiment, the carbohydrate is one that is attached directly or indirectly to a protein through a glycosylation reaction in a cell. In one embodiment, the carbohydrate is an N-linked carbohydrate or an O-linked carbohydrate. In yet another embodiment, the carbohydrate is N-azidoacetylgalactosamine, N-azidoacetyl-D-mannosamine, or N-azidoacetylglucosamine.

In certain embodiments, the azide-modified carbohydrate contains a moiety that facilitates entry into the cell including, but not limited to, a tetraacetyl moiety. Thus, in one embodiment, the azide-modified carbohydrate is a tetraacetylated version of an N-linked carbohydrate or an O-linked carbohydrate. In yet another embodiment, the azide-modified carbohydrate is tetraacetylated N-azidoacetylgalactosamine, tetraacetylated N-azidoacetyl-D-mannosamine, or tetraacetylated N-azidoacetylglucosamine.

In other embodiments, the azide-modified biomolecule is a fatty acid or a pharmaceutically acceptable derivative or prodrug thereof. The fatty acid can be selected from a wide variety of fatty acids commercially available and/or widely known to those skilled in the art. In preferred embodiments, the fatty acid is selected to prevent, inhibit and/or retard viral infection of cells. Preferably the fatty acid is naturally occurring.

In one embodiment, the fatty acid is saturated or unsaturated and has a hydrocarbon chain with an even number of carbon atoms, such as 4-24 carbon atoms. Suitable unsaturated free fatty acids have a hydrocarbon chain with 14-24 carbon atoms and include palmitoleic acid, oleic acid, linoleic acid, alpha and gamma linolenic acid, arachidonic acid, eicosapentaenoic acid and tetracosenoic acid. Suitable saturated fatty acids have a hydrocarbon chain with 4-18 carbon atoms and are preferably selected from butyric or isobutyric acid, succinic acid, caproic acid, adipic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid stearic acid, and arachidic acid. It is appreciated that the azide-containing fatty acid, whether naturally occurring or not, may be modified by chemical substitution including, but not limited to, short chain alkylation such as methylation or acetylation, esterification, as well as other derivitisations that maintain antiviral activity. In addition, it is possible to replace the fatty acid in the azide-modified biomolecule with an alkyne, ketone, or other small molecule that has been shown to be metabolically compatible.

In one embodiment, the fatty acid is one that is attached to a protein through an acylation reaction (e.g., palmitoylation or myristoylation) in a cell. Thus, in one embodiment, the azide-modified fatty acid is a saturated fatty acid, such as 15-azidopentadecanoic acid (palmitic acid, azide) or 12-azidododecanoic acid (myristic acid, azide).

In yet another embodiment, the azide-modified biomolecule is an azide-modified isoprenoid lipid or a pharmaceutically acceptable derivative or prodrug thereof. The isoprenoid lipid can be selected from a wide variety of isoprenoid lipids commercially available and/or widely known to those skilled in the art. In preferred embodiments, the isoprenoid lipid is selected to prevent, inhibit and/or retard viral infection of cells. Preferably the isoprenoid lipid is naturally occurring. It is appreciated that the azide-containing isoprenoid lipid, whether naturally occurring or not, may be modified, for example, by short chain alkylation such as methylation or acetylation, esterification, as well as other derivitisations that maintain antiviral activity.

In one embodiment, the isoprenoid lipid is one that is attached to a protein through a prenylation reaction in a cell. In one embodiment, the isoprenoid lipid, in the presence of the catalytic activity of a farnesyltransferase or a geranylgeranyltransferase, is attached to a protein in a cell. In another embodiment, the isoprenoid lipid comprises a farnesyl group or a geranylgeranyl group and includes, but is not limited to, an azido farnesyl diphosphate, an azido farnesyl alcohol, an azido geranylgeranyl diphosphate, or an azido geranylgeranyl alcohol.

The azide-modified carbohydrates, azide-modified fatty acids, and azide-modified isoprenoid lipids described herein can be prepared using methods known in the art, including those disclosed in U.S. Patent Application Publication No. 20050222427, U.S. Patent Application Publication No. 2007/0249014, and Hang, H. C. et al., J Am Chem Soc 2007, 129:2744-45, the disclosures of which are incorporated by reference in their entirety.

Combination Therapy

In one embodiment, a pharmaceutical composition comprising an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid and at least one anti-viral agent is administered in combination therapy. The therapy is useful for treating viral infections, including, but not limited to, an HIV infection. The term “in combination” in this context means that the azide-modified fatty acid, azide-modified carbohydrate, or the azide-modified isoprenoid lipid and the anti-viral agent are given substantially contemporaneously, either simultaneously or sequentially. In one embodiment, if given sequentially, at the onset of administration of the second compound, the first of the two compounds is still detectable at effective concentrations at the site of treatment. In another embodiment, if given sequentially, at the onset of administration of the second compound, the first of the two compounds is not detectable at effective concentrations at the site of treatment.

For example, the combination therapy can include an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid co-formulated with, and/or co-administered with, at least one additional anti-viral agent. Although specific examples of anti-viral agents are provided, in principle, the azide-modified fatty acid, azide-modified carbohydrate, or an azide-modified isoprenoid lipid can be combined with any pharmaceutical composition useful for treating a viral infection. Such combination therapies may advantageously use lower dosages of the administered therapeutic agents, thus avoiding possible toxicities or complications associated with the various monotherapies. Moreover, the additional anti-viral agents disclosed herein act on pathways or stage of viral infection in addition to or that differ from the pathway stage of viral infection affected by the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid, and thus are expected to enhance and/or synergize with the effects of the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid. The additional anti-viral agent may include at least one reverse transcriptase inhibitor, a virus protease inhibitor, a viral fusion inhibitor, a viral integrase inhibitor, a glycosidase inhibitor, a viral neuraminidase inhibitor, an M2 protein inhibitor, an amphotericin B, hydroxyurea, α-interferon, β-interferon, γ-interferon, and an antisense oligonucleotide.

The at least one reverse transcriptase inhibitor includes, but is not limited to, one or more nucleoside analogs, such as Zidovudine (AZT), Didanosine (ddI), Zalcitabine (ddC), Stavudine (d4T), Lamivudine (3TC), Abacavir (ABC), Emtricitabine (FTC), Entecavir (INN), Apricitabine (ATC), Atevirapine, ribavirin, acyclovir, famciclovir, valacyclovir, ganciclovir, and valganciclovir; one or more nucleotide analogs, such as Tenofovir (tenofovir disoproxil fumarate), Adefovir (bis-POM PMPA), PMPA, and cidofovir; or one or more non-nucleoside reverse transcriptase inhibitors, such as Efavirenz, Nevirapine, Delavirdine, and Etravirine.

The at least one viral protease inhibitor includes, but is not limited to, tipranavir, darunavir, indinavir, lopinavir, fosamprenavir, atazanavir, saquinavir, ritonavir, indinavir, nelfinavir, and amprenavir.

The at least one viral fusion inhibitor includes, but is not limited to a CD4 antagonist, such as soluble CD4 or an antibody that binds to CD4, such as TNX-355, BMS-806; a CCR5 antagonist, such as SCH-C, SCH-D, UK-427,857, maraviroc, vicriviroc, or an antibody that binds to CCR5, such as PRO-140; a CXCR4 antagonist, such as, AMD3100 or AMD070; or an antagonist of gp41, such as enfuvirtide.

The at least one viral integrase inhibitor includes, but is not limited to, raltegravir.

The at least one glycosidase inhibitor includes, but is not limited to, SC-48334 or MDL-28574.

The at least one viral neuraminidase inhibitor includes, but is not limited to, oseltamivir, peramivir, zanamivir, and laninamivir. Neuraminidase is a protein on the surface of influenza viruses that mediates the virus' release from an infected cell. (Bossart-Whitaker et al., J Mol Biol, 1993, 232:1069-83). The influenza virus attaches to the cell membrane using the viral hemagglutinin protein. The hemagglutinin protein binds to sialic acid moieties found on glycoproteins in the host cell's membranes. In order for the virus to be released from the cell, neuraminidase must enzymatically cleave the sialic acid groups from the host glycoproteins. Thus, inhibiting neuraminidase prevents the release of the influenza virus from an infected cell.

The at least one M2 inhibitor includes, but is not limited to, amantadine and rimantidine. M2 is an ion channel protein found in the viral envelope of the influenza virus (Henckel et al., J Biol Chem, 1998, 273:6518-24). The M2 protein plays an important role in controlling the uncoating of the influenza virus, leading to the release of the virion contents into the host cell cytoplasm. Blocking M2 inhibits viral replication.

An azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid disclosed herein can be used in combination with other therapeutic agents to treat specific viral infections as discussed in further detail below.

Non-limiting examples of agents for treating an HIV infection, with which the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid can be combined include at least one of the following: Zidovudine (AZT), Didanosine (ddI), Zalcitabine (ddC), Stavudine (d4T), Lamivudine (3TC), Abacavir (ABC), Emtricitabine (FTC), Entecavir (INN), Apricitabine (ATC), Tenofovir (tenofovir disoproxil fumarate), Adefovir (bis-POM PMPA) Efavirenz, Nevirapine, Delavirdine, Etravirine, tipranavir, darunavir, indinavir, lopinavir, fosamprenavir, atazanavir, saquinavir, ritonavir, indinavir, nelfinavir, amprenavir, a CD4 antagonist, such as soluble CD4 or an antibody that binds to CD4, such as TNX-355, BMS-806, a CCR5 antagonist, such as SCH-C, SCH-D, UK-427,857, maraviroc, vicriviroc, or an antibody that binds to CCR5, such as PRO-140, a CXCR4 antagonist, such as, AMD3100 or AMD070, or an antagonist of gp41, such as enfuvirtide.

Specific examples of combination therapy that can be used to treat HIV infection include, but are not limited to, an azide-modified fatty acid, azide-modified carbohydrate, or the azide-modified isoprenoid lipid combined with: 1) tenofovir, emtricitabine, and efavirenz; 2) lopinavir and ritonavir; 3) lamivudine and zidovudine; 4) abacavir, lamivudine, and zidovudine; 5) lamivudine and abacavir; or 6) tenofovir and emtricitabine.

Non-limiting examples of agents for a herpesvirus infection with which the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid can be combined include acyclovir, famciclovir, valacyclovir, cidofovir, foscarnet, ganciclovir, and valganciclovir.

Non-limiting examples of agents for an influenza virus infection with which the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid can be combined include amantadine, rimantidine, oseltamivir, peramivir, zanamivir, and laninamivir.

Non-limiting examples of agents for a respiratory synctial virus infection with which the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid can be combined include ribavirin.

Another aspect of the present invention accordingly relates to kits for carrying out the combined administration of the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid with other therapeutic agents. In one embodiment, the kit comprises the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid formulated in a pharmaceutical excipient, and at least one anti-viral agent, formulated as appropriate in one or more separate pharmaceutical preparations.

Pharmaceutical Compositions and Methods of Administration

This disclosure provides compositions that are suitable for pharmaceutical use and administration to patients. The pharmaceutical compositions comprise an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid and a pharmaceutically acceptable excipient. In one embodiment, the azide-modified fatty acid is a saturated fatty acid, such as 15-azidopentadecanoic acid or 12-azidododecanoic acid. In another embodiment, the azide-modified carbohydrate is an N-linked carbohydrate or an O-linked carbohydrate. In yet another embodiment, the azide-modified carbohydrate is N-azidoacetylgalactosamine, N-azidoacetyl-D-mannosamine, or N-azidoacetylglucosamine. In another embodiment, the azide-modified carbohydrate contains a moiety that facilitates entry into the cell including, but not limited to, a tetraacetyl moiety. Thus, in one embodiment, the azide-modified carbohydrate is a tetraacetylated version of an N-linked carbohydrate or an O-linked carbohydrate. In yet another embodiment, the azide-modified carbohydrate is tetraacetylated N-azidoacetylgalactosamine, tetraacetylated N-azidoacetyl-D-mannosamine, or tetraacetylated N-azidoacetylglucosamine. In another embodiment, the isoprenoid lipid comprises a farnesyl or a geranylgeranyl group and includes, but is not limited to, an azido farnesyl diphosphate, an azido farnesyl alcohol, an azido geranylgeranyl diphosphate, or an azido geranylgeranyl alcohol. The pharmaceutical compositions may also be included in a container, pack, or dispenser together with instructions for administration.

A pharmaceutical composition is formulated to be compatible with its intended route of administration. Methods to accomplish the administration are known to those of ordinary skill in the art. Pharmaceutical compositions may be topically or orally administered, or capable of transmission across mucous membranes. Examples of administration of a pharmaceutical composition include oral ingestion or inhalation. Administration may also be intravenous, intraperitoneal, intramuscular, intracavity, subcutaneous, cutaneous, or transdermal.

Solutions or suspensions used for intradermal or subcutaneous application typically include at least one of the following components: a sterile diluent such as water, saline solution, fixed oils, polyethylene glycol, glycerine, propylene glycol, or other synthetic solvent; antibacterial agents such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating agents such as ethylenediaminetetraacetic acid (EDTA); buffers such as acetate, citrate, or phosphate; and tonicity agents such as sodium chloride or dextrose. The pH can be adjusted with acids or bases. Such preparations may be enclosed in ampoules, disposable syringes, or multiple dose vials.

Solutions or suspensions used for intravenous administration include a carrier such as physiological saline, bacteriostatic water, Cremophor EL™ (BASF, Parsippany, N.J.), ethanol, or polyol. In all cases, the composition must be sterile and fluid for easy syringability. Proper fluidity can often be obtained using lecithin or surfactants. The composition must also be stable under the conditions of manufacture and storage. Prevention of microorganisms can be achieved with antibacterial and antifungal agents, e.g., parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, etc. In many cases, isotonic agents (sugar), polyalcohols (mannitol and sorbitol), or sodium chloride may be included in the composition. Prolonged absorption of the composition can be accomplished by adding an agent which delays absorption, e.g., aluminum monostearate and gelatin.

Oral compositions include an inert diluent or edible carrier. The composition can be enclosed in gelatin or compressed into tablets. For the purpose of oral administration, the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid can be incorporated with excipients and placed in tablets, troches, or capsules. Pharmaceutically compatible binding agents or adjuvant materials can be included in the composition. The tablets, troches, and capsules, may contain (1) a binder such as microcrystalline cellulose, gum tragacanth or gelatin; (2) an excipient such as starch or lactose, (3) a disintegrating agent such as alginic acid, Primogel, or corn starch; (4) a lubricant such as magnesium stearate; (5) a glidant such as colloidal silicon dioxide; or (6) a sweetening agent or a flavoring agent.

The composition may also be administered by a transmucosal or transdermal route. Transmucosal administration can be accomplished through the use of lozenges, nasal sprays, inhalers, or suppositories. Transdermal administration can also be accomplished through the use of a composition containing ointments, salves, gels, or creams known in the art. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used.

For administration by inhalation, the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid are delivered in an aerosol spray from a pressured container or dispenser, which contains a propellant (e.g., liquid or gas) or a nebulizer. In certain embodiments, the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid is prepared with a carrier to protect the compounds against rapid elimination from the body. Biodegradable polymers (e.g., ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, polylactic acid) are often used. Methods for the preparation of such formulations are known by those skilled in the art.

In other embodiments, the composition comprises a delivery agent for delivering the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid to a cell including but not limited to, a liposome. Liposomes (also known as lipid vesicles) are colloidal particles that are prepared from polar lipid molecules derived either from natural sources or chemical synthesis. Such spherical, closed structures composed of curved lipid bilayers, are typically used to entrap drugs, which are often cytotoxic, in order to reduce toxicity and/or increase efficacy. Liposome-entrapped drug preparations are often provided in a dry (e.g. freeze-dried) form, which is subsequently reconstituted with an aqueous solution immediately prior to administration. This is done in order to minimize the possibility of leakage of e.g. cytotoxic drug into aqueous solution and thereby reducing the entrapping effect of the liposome.

Examples of formulations comprising inter alia liposome-encapsulated active ingredients are discussed in U.S. Pat. No. 4,427,649, U.S. Pat. No. 4,522,811, U.S. Pat. No. 4,839,175, U.S. Pat. No. 5,569,464, EP 249 561, WO 00/38681, WO 88/01862, WO 98/58629, WO 98/00111, WO 03/105805, U.S. Pat. No. 5,049,388, U.S. Pat. No. 5,141,674, U.S. Pat. No. 5,498,420, U.S. Pat. No. 5,422,120, WO 87/01586, WO 2005/039533, US 2005/0112199 and U.S. Pat. No. 6,228,393, all of which are hereby incorporated by reference in their entirety.

The azide-modified fatty acid, azide-modified carbohydrate, or azide-modified isoprenoid lipid containing compositions are administered in therapeutically effective amounts as described. Therapeutically effective amounts may vary with the subject's age, condition, sex, and severity of medical condition. Appropriate dosage may be determined by a physician based on clinical indications. The azide-modified fatty acid, azide-modified carbohydrate, or azide-modified isoprenoid lipid containing composition may be given as a bolus dose to maximize the circulating levels of the azide-modified fatty acid, azide-modified carbohydrate, or the azide-modified isoprenoid lipid for the greatest length of time. Continuous infusion may also be used after the bolus dose.

Examples of dosage ranges that can be administered to a subject can be chosen from: 1 μg/kg to 20 mg/kg, 1 μg/kg to 10 mg/kg, 1 μg/kg to 1 mg/kg, 10 μg/kg to 1 mg/kg, 10 μg/kg to 100 μg/kg, 100 μg/kg to 1 mg/kg, 250 μg/kg to 2 mg/kg, 250 μg/kg to 1 mg/kg, 500 μg/kg to 2 mg/kg, 500 μg/kg to 1 mg/kg, 1 mg/kg to 2 mg/kg, 1 mg/kg to 5 mg/kg, 5 mg/kg to 10 mg/kg, 10 mg/kg to 20 mg/kg, 15 mg/kg to 20 mg/kg, 10 mg/kg to 25 mg/kg, 15 mg/kg to 25 mg/kg, 20 mg/kg to 25 mg/kg, and 20 mg/kg to 30 mg/kg (or higher). These dosages may be administered daily, weekly, biweekly, monthly, or less frequently, for example, biannually, depending on dosage, method of administration, disorder or symptom(s) to be treated, and individual subject characteristics. Dosages can also be administered via continuous infusion (such as through a pump). The administered dose may also depend on the route of administration. For example, subcutaneous administration may require a higher dosage than intravenous administration.

In certain circumstances, it may be advantageous to formulate compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited for the patient. Each dosage unit contains a predetermined quantity of azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid calculated to produce a therapeutic effect in association with the carrier. The dosage unit depends on the characteristics of the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid and the particular therapeutic effect to be achieved.

Toxicity and therapeutic efficacy of the composition can be determined by standard pharmaceutical procedures in cell cultures or experimental animals, e.g., determining the LD₅₀ (the dose lethal to 50% of the population) and the ED₅₀ (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD₅₀/ED₅₀.

The data obtained from the cell culture assays and animal studies can be used to formulate a dosage range in humans. The dosage of these compounds may lie within the range of circulating concentrations of the azide-modified fatty acid, azide-modified carbohydrate, or azide-modified isoprenoid lipid in the blood, that includes an ED₅₀ with little or no toxicity. The dosage may vary within this range depending upon the dosage composition form employed and the route of administration. For any azide-modified fatty acid, azide-modified carbohydrate, or azide-modified isoprenoid lipid used in the methods described herein, the therapeutically effective dose can be estimated initially using cell culture assays. A dose may be formulated in animal models to achieve a circulating plasma concentration range that includes the IC₅₀ (i.e., the concentration of antibody which achieves a half-maximal inhibition of symptoms). The effects of any particular dosage can be monitored by a suitable bioassay.

The compositions may also contain other active compounds providing supplemental, additional, or enhanced therapeutic functions. In one embodiment, the composition further comprises at least one anti-viral agent, such as a reverse transcriptase inhibitor, a virus protease inhibitor, a viral fusion inhibitor, a viral integrase inhibitor, a glycosidase inhibitor, an amphotericin B, hydroxyurea, α-interferon, β-interferon, γ-interferon, and an antisense oligonucleotide.

In one embodiment, the at least one reverse transcriptase inhibitor includes, but is not limited to, one or more nucleoside analogs, such as Zidovudine (AZT), Didanosine (ddI), Zalcitabine (ddC), Stavudine (d4T), Lamivudine (3TC), Abacavir (ABC), Emtricitabine (FTC), Entecavir (INN), Apricitabine (ATC), Atevirapine, ribavirin, acyclovir, famciclovir, valacyclovir, ganciclovir, and valganciclovir; one or more nucleotide analogs, such as Tenofovir (tenofovir disoproxil fumarate), Adefovir (bis-POM PMPA), PMPA, and cidofovir; or one or more non-nucleoside reverse transcriptase inhibitors, such as Efavirenz, Nevirapine, Delavirdine, and Etravirine.

In other embodiments, the at least one viral protease inhibitor includes, but is not limited to, tipranavir, darunavir, indinavir, lopinavir, fosamprenavir, atazanavir, saquinavir, ritonavir, indinavir, nelfinavir, and amprenavir.

In other embodiments, the at least one viral fusion inhibitor includes, but is not limited to a CD4 antagonist, such as soluble CD4 or an antibody that binds to CD4, such as TNX-355, BMS-806; a CCR5 antagonist, such as SCH-C, SCH-D, UK-427,857, maraviroc, vicriviroc, or an antibody that binds to CCR5, such as PRO-140; a CXCR4 antagonist, such as, AMD3100 or AMD070; or an antagonist of gp41, such as enfuvirtide.

In other embodiments, the at least one viral integrase inhibitor includes, but is not limited to, raltegravir.

In other embodiments, the at least one glycosidase inhibitor includes, but is not limited to, SC-48334 or MDL-28574.

Reference will now be made in detail to various exemplary embodiments. It is to be understood that the following detailed description is provided to give the reader a fuller understanding of certain embodiments, features, and details of aspects of the invention, and should not be interpreted as a limitation of the scope of the invention.

Example 1 Labeling HIV with Azide-Modified Biomolecules

CEMx174 cells were transfected with HIV_(NL4-3) in a T-150 flask and the virus production was monitored by reverse transcriptase activity until peak virus production occurred (usually 7 to 9 days post transfection). Prior to transfection, the CEMx174 cells were spiked with the following azide-modified biomolecules: 15-azidopentadecanoic acid (50-100 μM), 12-azidododecanoic acid (50-100 μM), tetraacetylated N-azidoacetylgalactosamine (20-40 μM), and tetraacetylated N-azidoacetyl-D-mannosamine (20-40 μM).

Infected cells were harvested at 12, 24, 72 hours, and 14 days. Harvested cells were isolated and lysed. Cell lysates were then mixed with the CLICK-IT® detection reagent, tetramethylrhodamine (TAMRA) alkyne and the CLICK-IT® Protein Reaction Buffer Kit (Invitrogen, Carlsbad, Calif.). Cell lysate samples were run on a one-dimensional gel to monitor changes in the azide labeled proteins over time (FIG. 1).

Labeled virus was also obtained from the transfected cells. More specifically, virus-containing supernatants were collected and virus was purified through 20% sucrose as previously described (Graham, D. R. et al., Proteomics 2008, 8:4919-30). The purified virus was then mixed with the CLICK-IT® detection reagent, tetramethylrhodamine (TAMRA) alkyne and the CLICK-IT® Protein Reaction Buffer Kit (Invitrogen, Carlsbad, Calif.). Virus samples were run on a one-dimensional gel to reveal azide-labeled viral proteins (FIG. 2). Virus levels were normalized p24 content and by one-dimensional gel electrophoresis.

No apparent effects of acute or chronic replication of HIV on host cellular protein modifications were observed (FIG. 1, compare label to controls). The azide-modified biomolecules, however, did label viral proteins and permit their detection at the expected molecular weights for HIV viral proteins: 55 KDa (gag-myristoylated); 41 KDa (gp41-palmitoylated) and 120 KDa (gp120-N-glycosylated) at 14 days in chronically infected cells (FIG. 1).

Example 2 Inhibiting Infectivity of HIV

To examine the effect of the azide-modified biomolecules on the innate biology of the virus, the azide-labeled virus from the transfected cells was isolated and tested in cell infection studies. Unlabeled HIV, at a concentration 100 times less than the test samples, was used as a control. Viral loads were normalized to p24 abundance and virus incubated for 12 hours on a reporter cell line (TZM/BI). TZM/BI is a genetically engineered HeLa cell line that expresses CD4, CXCR4 and CCR5 and contains Tat-inducible luciferase and β-Gal reporter genes. Viral infectivity was determined by measuring cellular luciferase activities with two different luciferase reagents. The results using a single cycle replication system showed that virus labeled with the azide-modified biomolecules, particularly 12-azidododecanoic acid, and to a lesser extent, 15-azidopentadecanoic acid and tetraacetylated N-azidoacetylgalactosamine, had a profound impact on the infectivity of the virus (FIGS. 3 and 4). The level of inhibition of viral entry observed was comparable to the level of inhibition observed in cells pre-treated with an anti-retroviral agent, such as a fusion inhibitor or a nucleoside analogue.

Example 3 Toxicity Profile

Little to no toxicity has been observed when using these azide-modified biomolecules in various eukaryotic cell lines, suggesting that these compounds have a minimal toxicity profile and supporting their use in a therapeutic setting. 

1. A method of producing a human immunodeficiency virus labeled with an azide-modified fatty acid, an azide-modified carbohydrate, or an azide-modified isoprenoid lipid, the method comprising contacting a cell infected with the human immunodeficiency virus with the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid so that the azide-modified fatty acid, the azide-modified carbohydrate, or the azide-modified isoprenoid lipid enters the cell and is incorporated into a protein of the virus, thereby producing the labeled virus.
 2. The method of claim 1, wherein the azide-modified fatty acid is a saturated fatty acid.
 3. The method of claim 1, wherein the azide-modified fatty acid is 15-azidopentadecanoic acid.
 4. The method of claim 1, wherein the azide-modified fatty acid is 12-azidododecanoic acid.
 5. The method of claim 1, wherein the azide-modified carbohydrate is an N-linked carbohydrate or an O-linked carbohydrate.
 6. The method of claim 1, wherein the azide-modified carbohydrate is tetraacetylated N-azidoacetylgalactosamine, tetraacetylated N-azidoacetyl-D-mannosamine, or tetraacetylated N-azidoacetylglucosamine.
 7. The method of claim 1, wherein the azide-modified isoprenoid lipid comprises a farnesyl group or a geranylgeranyl group.
 8. The method of claim 7, wherein the azide-modified isoprenoid lipid is an azido farnesyl diphosphate, an azido farnesyl alcohol, an azido geranylgeranyl diphosphate, or an azido geranylgeranyl alcohol.
 9. The method of any one of claims 1-8, wherein the cell is a human cell. 